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Technical Tips & Information
Flow Measurement
Foxboro offers a broad range of flow measurement devices for steam, air, water, gas, and most other fluids. Vortex meters measure flow by allowing the fluid or gas to be measured to pass through a thin wing like bar which vibrates as a result of the vortices being shed. Think of a flag flapping in the breeze. The stronger the wind, the more the flag will flap or shed vortices. A transducer measures this rate of vibration and converts it to an electrical signal for flow measurement.For many applications a vortex meter is ideal since it introduces virtually no pressure drop in the stream being measured. Turn down is the ability to read over a wide range. Many other styles of flow measurement devices have turn down ratios of 5-10:1. Vortex meters have turn downs in the range of 20:1 or higher. High turn down means that a much broader range of flow values can be measured.
Flow meters must be properly sized to match the flow range to be measured. In many cases the actual meter size will be smaller than the line into which the unit is being inserted. To properly apply a meter, you should have a good feel of the range of flows to be measured.
Flow meters ultimately compare a reading to the density of the fluid or gas being measured. All gas densities will vary as a function of pressure and temperature. If you expect the pressure or temperature in your application to vary, then these values must also be measured and incorporated into the final calculations at the meter to arrive at a flow rate.
Once the flow has been converted to a signal, a dedicated computer is used to convert the meter signal or signals to a flow measurement. Flow computers typically provide reading for both flow rate as well as totalizing the flow values. If pressure or temperature compensation is part of your application, the flow computer will correct for changes in these values to provide an accurate flow measurement. Flow computers can also provide signals to be transmitted to other computers in your plant or facility.
If flow measurement is in your future, call us to discuss application details and options.